OAKLAND -- For the second time in three weeks, Dinyal New is preparing to bury a slain son.

On Monday, she wept as she placed flowers on the East Oakland sidewalk near where her 19-year-old son and his best friend were shot dead. New kicked at the broken glass at the double homicide scene, still numb from burying her 13-year-old just four days earlier.

"I have no more kids," New told reporters.

Each son was killed within blocks of New's East Oakland home.

Her heartbreak began on New Year's Eve, when Lee Weathersby III was fatally shot while walking home. Earlier in the day, he had attended a party at the Boys & Girls Club of Oakland on International Boulevard. He died in the early morning hours of New Year's Day.

Lee was a popular student who played basketball and was a drummer in the school band.

On Sunday afternoon, his older brother, Lamar Broussard, and Derryck Harris, both 19, were shot and killed while driving, marking the city's fourth and fifth homicides of 2014.

As she stood at the site where Broussard died, New said she could not imagine a link between the killings of her sons and said no one outside the family knew they were brothers.

Investigators have not ruled out the possibility that Sunday's homicides are linked to an ongoing dispute over the death of the younger brother. The shooting was not random, authorities said. No arrests have been made.

Broussard and Harris left New's home about 2:15 p.m to go pay New's cellphone bill, the mother said. They did not get far -- some two blocks -- before family and friends say gunmen ambushed them, unloading a hail of gunfire on the car.

Shakia Green, Broussard's cousin, said she believes the gunmen were watching for the pair of 19-year-olds.

"This is just back-to-back for me," Green, of Oakland, said, sharing the pain of dealing with another death. "I can't do it."

Harris' family could not be reached Monday.

A makeshift memorial marked the shooting scene Monday. Friends and family brought stuffed animals, left notes and lit candles. The teens' nicknames "MarMar" and "Lil D" were spelled out in tea lights.

The two had been friends since they were toddlers and considered each other "godbrothers," family and friends said.

Broussard had recently re-enrolled at Laney College, where he planned to study music. He dreamed of someday starting his own business, New said. Classes begin Tuesday.

Family members were also in the process of helping Broussard move to another part of Oakland to help him escape the violence of his neighborhood. The mother said both her sons were "caring" and "God-fearing boys."

File: Dinyal New, mother of slain teenager Lee Weathersby III, prepares to speak at a memorial service for her son held at Alliance Academy in Oakland, Calif. on Wednesday, Jan. 8, 2014. (Kristopher Skinner/Bay Area News Group)

She called on witnesses to the three killings to step forward to help detectives make arrests. New also said she hopes there will be no retaliation for her sons' killings, urging that her sons' killers be tried in the courts -- not on the streets.

Broussard attended his younger brother's funeral last week. He was also the one who identified his brother for authorities.

New said she can't bring herself to look at her sons' bodies.

"I don't even have the courage to go and identify my baby," she said. "Somebody else has to go because I just have to remember them exactly the way they were."